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Cross-site Scripting occurrences in Hydrogen
Hydrogen is a React-based framework for building dynamic, Shopify-powered custom storefronts. There is a potential Cross-Site Scripting (XSS) vulnerability where an arbitrary user is able to execute scripts on pages that are built with Hydrogen. This affects all versions of Hydrogen starting from version 0.10.0 to 0.18.0. This vulnerability is exploitable in applications whose hydrating data is user controlled. All Hydrogen users should upgrade their project to version 0.19.0. There is no current workaround, and users should update as soon as possible. Additionally, the Content Security Policy is not an effective mitigation for this vulnerability. (2022-05-18, CVE-2022-29230)
Why Cross-site Scripting can be dangerous
Cross site scripting is an attack where a web page executes code that is injected by an adversary. It usually appears, when users input is presented. This attack can be used to impersonate a user, take over control of the session, or even steal API keys.
The attack can be executed e.g. when you application injects the request parameter directly into the HTML code of the page returned to the user:
https://server.com/confirmation?message=Transaction+Complete
what results in:
<span>Confirmation: Transaction Complete</span>
In that case the message can be modified to become a valid Javascript code, e.g.:
https://server.com/confirmation?message=<script>dangerous javascript code here</script>
and it will be executed locally by the user's browser with full access to the user's personal application/browser data:
<span>Confirmation: <script>dangerous javascript code here</script></span>